My problems definatly an over-cooling issue.... I live right by the interstate it takes 10-15 minute of 80mph speeds for my engine to get to norm operating temp... the it will cool down and kick back out of OD then if i'm driving far it takes about 5 minutes to heat back up and kick OD back in and so on......

* replaced therm w/ new OE.--> NO IMPROVMENT

My fan clutch doesnt seem to be stuck...

Ive never heard of such a problem!!! I hate to replace the temp sensors they seem to be doing there job... there are two sensors (1 for gauge 1 for comp) right i guess I should check that... hmmm....

 

You may have a bubble in the cooling system at the temp sensor. Won't let the coolant get right up to it, so it's not getting enough heat unless you're running it hard.

Try burping the radiator hoses, engine idling (but cool enough to take the radiator cap off). This may take some time. It's worth a shot.

Mike in AR

 

thnx i'll try that on my day off

 

maybe the thermo is installed upside down?

 

After I did a radiator flush I had a lot of air in there, and mine had a hard time getting up to temp as well, like Mike said.

Check it out.

 

UPSIDE DOWN?!?!?!?!?!?! is that possible I hope not.....

 

Yep. Just flushed my rad/block and replaced the hoses/thermo/coolant this past Friday. The jiggle valve (small button near the outer edge of the thermo) should be 15°-20° off of 12 o'clock.

 

I have a 91 4runner with 3.0 and auto and mine does the exact same thing as yours with the temp and the down shifting out of overdrive I have changed thermostat also and still have not come to a conclusion. I will be watching to see if the burping the system works. good luck

 

maybe you need to check your thermostat it could be poping open too early.

also, does your fan keep spinning after startup? or does the clutch stop it from moving?

 

I Tried Burping For About Ten Minutes Couldnt Tell If I Was Getting Anywhere ... DINDT FIX ANYTHING I'LL TRY SOME MORE TOMARROW SINSE I'M OFF ... I'LL POST WHAT I FIND W/THE FAN CLUTCH.... AND AS FAR AS THE THERMO BEING UPSIDE DOWN... THE 91 3.0'S DONT HAVE A CHECK VALVE.... I REALIZED THIS AFTER I DUMPED HALF MY ANTI FREEZE ON THE GROUND THE SECOND TIME ... I WORK AT ADVANCE THAT CRAP IS STILL EXPENSIVE!!
MOST 3.0 OWNERS(THAT COME IN FOR PARTS) I TALK TO HAVE OVERHEATING ISSUES. THEY FREAK OUT AT MY OVERCOOLING SITUATION...

 

I know the feeling. I finally gave up and just put the cap on in the first position (half on, half off) and let it idle for 10 and I was good to go.

Some (Mike in AR) recommend getting the RPM's up a bit to burp it, IIRC.

Good luck.

 

I recently flushed and filled my 3.0. I used some Prestone Flush, so I had to do a seires of filling and flushing to get all the crud out. I burped mine every time I filled it , just to make sure it didn't accidentally get a bubble in it and overheat. I would hold the throttle open in the cab with engine RPMs at about 3,000. I wanted to be sure the water pump was pushing the water thru the system at its full capacity.

Mike in AR

 

Did you ever sort out your overcooling issue? Mine is doing the same thing, not the Thermostat. I have to block off 1/2 the rad with cardboard so the engine will run within O/D temp